Astronomers may have, for the first time, directly imaged a planet still in the process of formation, gathering material from a debris disk surrounding its parent star.

First: Holy Haleakala!

Second: note the use of the word "may". It looks to me like it’s real, though.

Third: Oh, you want to see the picture? Well, let me do the honors:

The alleged planet, called LkCa 15b, is the blue spot in the image. The red shows material which is most likely accumulating onto the planet itself, building up its mass. The central star isn’t seen in this image because its light has been blocked out so the fainter material near it can be seen. The star’s position is marked by the star icon.

The image is in the infrared, taken using the monster Keck telescope in Hawaii. What’s shown in red is light at a wavelength of 3.7 microns (roughly five times what the human eye can see) and blue is from 2.1 microns, about three times what we can see. Warm material around the star is best seen at these wavelengths. If this is a planet, it’s at a temperature of about 500 – 1000 K (440° – 1340° F), and has a mass roughly six times that of Jupiter, or about 2000 times the Earth’s mass.

So is it a planet? I read the journal paper (PDF) the astronomers wrote, and they make a pretty good case. It’s not a background object that’s aligned by chance with the star; they observed the system over the course of a year and the object is moving along with the star in the sky, so they’re clearly connected. The authors also very carefully eliminate other possible explanations (a low-mass star instead of a planet, a large clump of dust, reflected light from the star), and come to the conclusion that this data is best explained as a young planet in the act of forming. It looks pretty good to me… certainly enough so that I added it to my gallery of directly imaged exoplanets! To make things simple, from here on out in this post I’ll assume it’s real.

This is a pretty interesting system. The star, called LkCa 15, is only about 2 million years old, and about as massive as the Sun. It’s located pretty close to us as these things go, about 450 light years away in the constellation of Taurus. It’s known to have a pretty big disk of dust circling it — called a protoplanetary disk — stretching well over 20 billion km across. By comparison, Neptune’s orbit around the Sun is about 9 billion km across! So it’s a big disk.

Also? It has a hole in it. Here’s an image of the disk taken in the far infrared comparing the disk to the planet image:

[Click to protoplanetate.]

The disk’s hole is about 8 billion km across. Disks like this are seen around other stars, and it’s generally thought that the hole is caused by a planet orbiting inside that region sweeping up material. In this case, that looks to be true! If the planet is in a circular orbit, it’s about 2.5 billion kilometers from its star, a little closer to its star than Uranus is from the Sun (it’s not known if the orbit is circular or elliptical; that’ll take a few years of observations as the planet physically moves around the star and the orbit can be calculated). The planet is much hotter than you might expect, but that’s because it’s so young: material is falling onto it, heating it up. That’s why it’s glowing in the infrared.

If all this is hard to picture, here’s a nice artist’s illustration of the situation:

That should help. The star is in the center of the disk, with the planet orbiting in the cleared-out region. Material is still falling onto the planet, so it’s still physically in the process of forming.

Nothing like this has been seen before in a planet so young! That’s scientifically quite important. Our models of how planets form are complex, and we need detailed observations to see if the models are correct or not. Since planet formation is a process, we need observations of it at different stages, including very early on. That’s crucial, since it represents the transition period between the time before planets start to form in the disk, and the time when the planets are all finished and tidied up. We’ve seen both of those before, so this observation is a first.

All in all, very, very cool. Only a handful of planets have been directly imaged (see the gallery below), so even adding another single case is important; adding one at this stage in its birth process is fantastic.

We’ll be seeing more and more of these as time goes on. The astronomers, Kraus and Ireland, are planning more observations of LkCa 15… and it’s just one example of a star that’s forming in that region of space. They’ve targeted several others as well, so who knows what else they’ll find poking around in there?

[Below is a gallery of exoplanets that have been directly imaged using telescopes on ground and in space. Click the thumbnail picture to get a bigger picture and more information, and scroll through the gallery using the left and right arrows.]

Creationist acquaintances of mine always used to complain that there was no reason outside of speculation to accept the idea that planets gradually accrete around stars. That’s totally wrong, of course, but now we actually have pictures.

@6. Mark : “Aww, little baby planet. I hope you grow up big and strong and accrete lots and lots of moons that can potentially harbor life!”

It is hypothetically possible life could exist floating inside the gas giant’s atmosphere as speculated by writers such as Arthur C. Clarke and Ben Bova -and in rather different form again by george Lucas with Bespin! 😉

Pure speculation so far but still. There may be life not only in the ocean under the ice of Europa and moons elsewhere like it but inside the Jovians, superjovians like this and ice giants like Neptune too. Hot Jupiters and worlds that are currently forming a very big stretch given the extrmes and turbulence involved but, well, who knows. As Haldane (I think?) noted “the universe is not only stranger than we imagine but stranger than we *can* imagine.”

It will be interesting to see how this one holds up. The note of caution in this kind of thing comes courtesy of Fomalhaut b, which is not behaving as predicted: apparently its orbit may cross the system’s dust ring, which casts various doubts on what is actually being seen there.

Woohoo! I love this stuff!! I mean, I love all astronomy, but you have to admit that the planet-finding research is pretty high up on the “to Boldly Go” awesomeness scale.

I do have an offhanded question – it seems like many of the planetary systems we find are quite extreme by our standards. Jupiter is a darn big planet, but it seems like every other exoplanet is a super-Jupiter. And many of them are as far out as our kuiper belt or closer then Mercury. Is our solar system just plain weird? Or does it simply seem that way to me because I’m being, er, Heliocentric? 😉

Well, the techniques we currently have are best at identifying the most extreme systems, because those are the easiest to spot quickly. Big planets produce a stronger pull on their stars, and close orbiting planets create a faster wobble that requires very little time to identify. To spot the planets in the middle requires more sensitivity and/or more time to pin down the orbital period.

So it may be that these super systems are actually more common, or it may be instrumentation bias skewing the results.

Woohoo! I love this stuff!! I mean, I love all astronomy, but you have to admit that the planet-finding research is pretty high up on the “to Boldly Go” awesomeness scale.

I feel the same way too. Exoplanets are also my favourite area of astronomical discovery and it never ceases to amaze and delight me how we’re finding and what we’re finding out there in the Black. 😀

I do have an offhanded question – it seems like many of the planetary systems we find are quite extreme by our standards. Jupiter is a darn big planet, but it seems like every other exoplanet is a super-Jupiter. And many of them are as far out as our kuiper belt or closer then Mercury. Is our solar system just plain weird? Or does it simply seem that way to me because I’m being, er, Heliocentric?

Well, yes and no.

We *have* discovered a lot of strange exoplanetary systems and quite a number of superjovian worlds verging on brown dwarf status but we’ve also discovered a lot of exo-Saturns, exo-Neptunes and “super-Earth” type planets (which I’d describe more as Super-Venuses” given the majority are far hotter and more hostile than here.)too.

It isn’t just Superjovians or HotJupiters or Eccentric Orbiters and we know of systems with many gas giants that are smaller than Jupiter mass~wise. There’s at least a couple of systems that somewhat resemble our own including 47 Ursae Majoris and in a way, weirdly enough, PSR 1257+12.

As (#22.) HvP has pointed out its also partly at least a reflection of our technology and our selection sample is baised by what worlds are easiest to find. Detecting an earth-like planet in an earth-like orbit is something that’s still so staggeringly difficult and time taking to accomplish it’s probably no surprise it hasn’t been done yet.

The new exoplanets do tell us that many systems are very different to our own – that a lot of suns have Hot Jupiters and Eccentric Orbiters which renders them very unlikely to have habitable worlds in them.

OTOH, it shows us there are a huge variety and number of exoplanets out there orbiting almost every type of star and that Earths while perhaps rarer than we hoped for, are also likely to still be around in reasonably mind-blowing numbers. IOW, planets and planetary systems are relatively common and abundant.

We have reason to think that Alpha Centauri may well have rocky worlds, we know that systems like 47 Ursae Majoris exist which do have room for smaller planets in “Goldilocks” places, we know now-ornage giant star Pollux hosts a superjovian in a circular orbit which could mean it once hosted habitable worlds closer in when it was a somewhat more sun-like (or maybe more Procyon-like) star.

So there are both signs for hope and concern habitable earth-like planet~wise and we still have an awful lot more to discover before we can say much more than that. Insufficient data really still but were getting ever closer and ever more complete in our understanding of these new-found worlds of other stars.

In 2003, astronomers at the University of Texas at Arlington performed refined calculations to determine that the habitable zone around 47 Ursae Majoris, where an inner rocky planet (with suitable mass and atmospheric gas composition and density) can have liquid water on its surface, lies between 1.05 and 1.83 AUs of the star. They found that the development of an Earth-like planet in the inner portion of this zone may survive disruption from the development of known planetary candidates planet b and c. If a small, rocky planet can develop without the interference of planet b, then stable orbits appear to be possible in the inner portion of the habitable zone (Noble et al, 2002, in pdf; and Jones and Sleep, 2003). Subsequent analysis suggests that the habitability of such an inner rocky planet would be boosted if the star was “relatively young” at six or less billion years old and has a “relatively small stellar luminosity”

We don’t yet know of such an exoplanet but this could be a good bet for one of the nearest habitabile exoplanets. Behind only Alpha Centauri the very nearest star of all – well, almost, depending on whether Proxima Cen is really Alpha Cen C or independent anyhow.

Pretty sure there are a few other Jupiter analogues – Jovians in Jovian type orbits – that are known too.

“Of about 100 typical Sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune, and about 12 have super-Earths between three and 10 Earth masses,” said astronomer and lead author Andrew Howard, from the University of California at Berkeley. “If we extrapolate down to Earth-size planets – between one-half and two times the mass of Earth – we predict that you’d find about 23 for every 100 stars.”

Which is a positive albeit still uncertain sign too. Not sure if those rough estimate numbers have changed much since that was written but Kepler and CoROT are certanly finding stacks more exoplanets and taking the total of known exoplanets far higher quite quickly.

That does make it seem like lower mass exoplanets are more common than higher mass ones which matches nicely the way lower mass stars (&, for that matter, lower mass animals) are much more numerous than higher mass ones so, yeah, its not all Superjovians out there! 😉

Actually its good there are so many super-Jupiters out there, since they make great pit-stops for refuelling by ram-scoop. Gravity boost is icing on the cake- onward to the next system! Another Anthropic effect?

Still- a place like this LOOKS bright and shiny and new, til you realize that its hundreds of light years away, and by now the neighborhood has gone to the dogs.

@29. oPL : “In the artist’s impression it looks like the planet is bigger than its star. Fail.”

No, perspective. The Moon looks as big as the Sun from Earth when in fact its much smaller by about 400 times. Pluto looks bigger than the Sun by metaphorical miles – when you view it from the surface of Charon. A train on the horizon looks smaller than a moth flying a few centimeters from you. It’s all depends on your point of view! 😉

The section of the disc hole behind the star from our view seems roughly half as wide as the section in front of it. This is due to perspective.

If the planet were just in front of the star from our view, and aligned (which by the way it isn’t), then you would have a point.

However, in the picture we are seeing the whole system from an elevated position.

And in any case, with the current perspective, if we align the planet behind the star (where the disc hole is about half as wide as in front of the star) then wouldn’t it look about half its apparent front-of-the-star size?

That would still be much bigger than the star in the picture.

And the planet is at most at a 15º angle with the diametre of the perpendicular, from our view.

So either the planet is bigger than the star, or the perspective in the picture is wrong. Fail 😛

I’m amazed, knowing the usual level of pedantry we all engage in on here (it’s FUN), that nobody has pointed out yet that technically, it’s impossible for any orbit to be perfectly circular. Even though it’s clear what you mean – “near enough” circular, as in the orbits of Earth and the other planets, as opposed to something like Eris or even a comet. But still, I won’t be happy until it’s been pointed out.

Secondly I see little evidence of an actual forming planet, there is an equal amount of evidence that the dust is falling off the planet.

Thirdly and perhaps most damning to the evidence of a forming planet is that in 2009 a planetery formation study was done by Erik Asphaug of Univeristy of California Santa Cruz and found:
“Not only must turbulence be low, but the gas must go away before the growing planetesimals spiral in….”

The first link states that gas is present, and Asphaugs study shows that it can not be if planetesimals are to form.

I realize I’m about two months late on this, but I only recently heard about it. Sorry for the delay